I want to create a flotation device

[eNathan]

My idea is to create a flotation device that would have a strong electromagnet at the top, this pulling objects upwards, just enough to cancel out gravity. A computer software will determine how much power to send to the electromagnet by knowing exactly how close the object is to the electromagnet using sensors of some sort.

So basically, when the metalic object starts going upwards towards the electromagnet, the software will lower the power of the electromagnent to let it start to fall back down due to gravity. Then it powers back up once it gets a bit too low. If a fairly constant equillibrium can be reached, the object should appear to float (perhaps wobbling up and down a bit, however).

How would I do this? I'm a software engineer so I can handle that aspect of it. What type of sensors would I use to know how high the object is getting? Would it be realistically posible to have the computer software process that and lower the power to the electromagnent in just enough time? The only type of sensor I could think is a web cam, coupled with a software to process the images.

Also, I really don't understand much about electromagnetism, but I'm willing to learn. What equations do I need to learn and perhaps impliment? From my observation of magnents, it seems that once a metal object gets into a certian range, it just absolutly flies up to the magnent. It's not some sort of slow progression. What are the equations to express all this, like magnent strength, movement, etc? As the software would have to know exactly how to modify the power output.


(Note: Please, no unnessasary pessimism towards my project unless you have a genuine reason as to why it can't suceed.)

Thanks!

 

[Mapes]

A friend of a friend did http://bea.st/sight/lightbulb/" AND made it light by using wireless power transfer. I believe the feedback mechanism was a laser rangefinder shining from the bottom.

 

[eNathan]

Wow, that's really impressive! A laser rangefinder seems to be the right solution.. I'll have to do some research into where to buy one and how you could posibly incorperate it with a software program. All I find when searching for them are hunting binoculars. :P

Can anyone help me out with the mathematics though? I'm willing to research and experiment on my own, I just need a nudge in the right direction. Are all I need to understand are Maxwell's equations? Maybe just some equations to describe the acceleration of the metalic object given the strength and distance from the electromagnent, so that I can have an idea of how much strength needs to be given / taken away to keep it afloat.

 

[Naty1]

You need an electromagnet design that can support a weight of your choosing over a range of interaction you find satisfying.

Try "electromagnet" on Wikipedia for an overview with a few diagrams; then Google electromagnet design...you'll get a lot of hits and you can begin to decide what kind of electromagnet you'd like...

Would it be realistically posible to have the computer software process that and lower the power to the electromagnent in just enough time?

yes, but its a situation full of practical problems...It's likely this problem has been faced many times and some standard approaches developed...you'll have to decide if you want
to find them or do trial and error work on your own...

Once the mass begins to move the electromagnetic field needs enough power (force) to overcome momentum in addition to the fixed mass of the object. So your magnetic field has to overcome both over a distance of your choosing. A large and powerful magnetic field is not easy to produce in an experimental home lab setup...the bigger the field, the more electric power required. as you note , you vary the magnetic field strength by varying the electromagnet field current...the rate of change of field current will be limited by the inductance of the wire coil...how that limits response time to a moving weight determines your degree of control. You'll also have to decide how to power a laser range finder at it's required voltage as well as the larger power requirements (different voltage and current) of the electromagnet. Not a big deal, but you may need multiple power sources.

 

[Mapes]

And you're going to enter the exciting world of control theory. We can casually talk about controlling the field strength to keep the item stable, but control theory tells you how actually to do it. Feedback, poles, zeroes, stability, overshoot, damping... it's fantastic.

In undergrad I studied Nise's Control Systems Engineering. It's pretty good and worth checking out.

 

[bchandler]

You might want to crack one of these open. They're cheap and operate in the same way you are thinking:

http://www.gadgets-reviews.com/uimg_new/magnetic-floating-globe-10cm-diameter.jpg